1. Field
The present disclosure relates generally to antennas and, in particular, to phased array antennas. Still more particularly, the present disclosure relates to a phased array antenna having unit cells that are identical to each other.
2. Background
A phased array antenna is a group of antennas in which the relative phases of the respective waves sent to and from the antennas may be varied. The variant of the waves sent to and from the antennas is such that the effect of the radiation pattern of the antennas is reinforced in a desired direction and suppressed in undesired directions. In other words, one or more beams may be generated that may be pointed in or steered into different directions. A beam pointing in a transmit or receive phased array antenna is achieved by controlling the phasing timing of the transmitted or received signal from each antenna in the phased array antenna. The antennas in the phased array antenna may also be referred to as antenna elements.
The individual radiated waves are combined to form the constructive and destructive interference patterns of the array. A phased array antenna may be used to point one or more fixed beams or to scan one or more beams in azimuth, elevation, or both.
One of the advantages of phased array antennas is that these types of antenna designs are typically thinner than other types of antennas. For example, a phased array antenna may be manufactured having a shape that is thinner than a reflector antenna.
Reducing the size and/or weight of phased array antennas is often a desirable goal. For example, when a phased array antenna is used in an aircraft, a reduction in the size and weight of the phased array antenna may allow for maintaining or increasing performance of the aircraft. The performance that may be of interest may include, for example, without limitation, range, maximum speed, maximum altitude, and/or other types of performances.
In reducing the thickness of phased array antennas, the different electronic circuits are typically mounted in the same plane as the antenna elements. For example, if antenna elements are formed on one side of a plane or substrate, the electronic circuits may be formed on the other side of the substrate. Each antenna element is typically connected to one or more electronic circuits in a package.
The spacing of antenna elements is typically selected as at least about one half of a wavelength for the frequency being used. This selection is made to avoid a grating lobe. A grating lobe is a second main lobe in addition to the first main lobe that is in real space. It is desirable to avoid a second main lobe in transmitting electromagnetic waves in phased array antennas. As a result, a spacing of at least about one half of a wavelength is typically used.
As the frequency increases, the spacing between elements decreases. With currently available circuit designs and packaging for circuit designs, reducing the size of those electronic circuits may be challenging as the frequencies being used increases.
Therefore, it would be advantageous to have a method and apparatus for overcoming the problems described above.